Slide 1 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
Fundamentals of Health Workflow Process Analysis and
Redesign
Unit 10.3f
Process Mapping
Entity-Relationship Diagrams
Slide 2 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
Topics in this Sub-unit
• Background
• Process aspects covered
• Diagram use
• Symbols and notation conventions
• Reading a simple Entity-relationship diagram
• Maintenance
Slide 3 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
Background
Entity-Relationship Diagrams:• Are also called E-R diagrams or ERDs • were made popular by Peter Chen in a 1976 paper1 and
introduced by Charles Bachman in an earlier 1969 paper2
• represent data and the relationships between data values
• are data models • Are used to specify or document static content, i.e., data
that are stored in a data system– NOT process steps, step sequence, or flow control
Slide 4 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
Your Relationship with ERDs• As a workflow analyst, you will most likely not be
creating ERDs.• However, you may run into them as:
– documentation provided by a prospective vendor, or – documentation that a facility has for a system.
• Based on the relational data model – this course does not require relational database
knowledge– This course does not cover relational database topics
Therefore:• This sub-unit covers reading and interpreting
ERDs, not how to create them.
Slide 5 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
ERDs and UML
• ERDs and UML class diagrams basically represent the same thing: data and relationships between data values
• Use different notation • Both support multiple levels of abstraction and
inheritance • ERDs are often called data models • Class diagrams are referred to as information models
Slide 6 Health IT Workforce Curriculum
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Use
• ERDs are used to specify or document static content, i.e., – data that are or are to be stored in a data
system.– Databases are built from ERDs
Slide 7 Health IT Workforce Curriculum
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Notation
• Several notations exist for drawing ERDs, the most common is Barker, or “crows foot” notation.
• “crows foot” notation is generally favored because of its readability and more efficient use of drawing space3.
Slide 8 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
ERDs represent content:
1. Entities are things about which we collect and store data
2. Relationships describe how the data values are linked, how they fit together
3. Attributes are the actual pieces of data that we collect and store
Slide 9 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
An ERD Example
Student*student_idstudent_namestudent_address
Seat*seat_number
Instructor*instructor_numberinstructor_nameinstructor_department
Course*course_namecourse_numbercourse_credithrs
Section*section_numbersection_online
fills
registers for
teaches
has
Slide 10 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
Entity
• a person, place or thing, i.e., noun, about which we want to collect and store data
• has a name, attributes, and an identifier
• the identifier uniquely identifies an instance of an entity– The attribute which acts as the
identifier is marked with an asterisk.
Course*course_namecourse_numbercourse_credithrs
name
attributes}
entity
Slide 11 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
Relationship
• a relationship between two entities is represented by a line
• has a name which is a verb
• also has cardinality and modality
Course*course_namecourse_numbercourse_credithrs
Section*section_numbersection_online
has
relationship
Slide 12 Health IT Workforce Curriculum
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Cardinality and Modality
• Cardinality and Modality work together to define the relationship
• Cardinality indicates the maximum number of times an instance in one entity can be associated with instances in the related entity
• Modality indicates the minimum number of times an instance in one entity can be associated with an instance in the related entity
• Cardinality and Modality are both shown on the relationship line by symbols
Slide 13 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
Cardinality
• Cardinality → maximum • Cardinality can be 1 or Many • the symbol is placed on the
outside of the relationship line, closest to the entity – cardinality of 1 is represented by a
straight vertical line – cardinality of Many is represented by
a “crow’s foot”
• Cardinality is indicated at both ends of the relationship line
~~~~~
Slide 14 Health IT Workforce Curriculum
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Modality
• Modality → minimum • Modality can be 1 or 0• the symbol is placed on the
inside, next to the cardinality symbol – modality of 1 is represented by a
straight vertical line – modality of 0 is represented by a
circle
• Modality is indicated at both ends of the relationship line
~~~~~
Slide 15 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
Reading Modality and Cardinality
from Zero to Many
from One to Many
from One to One
i.e., one and only one
from Zero to One
Modality and cardinality are combined (two at a time) in these ways:
Slide 16 Health IT Workforce Curriculum
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StudentSeatfills
CourseInstructor teaches
CourseStudent Registers for
TranscriptStudenthas
Left to right: a seat is filled by exactly one studentRight to left: a student fills exactly one seat
Left to right: a student has one or more transcriptsRight to left: a transcript has one student
Left to right: a student registers for one or more coursesRight to left: a course is registered by one or more students
Left to right: an instructor teaches zero to many coursesRight to left: a course is taught by exactly one instructor
Reading Cardinality and Modality
Slide 17 Health IT Workforce Curriculum
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StudentSeatfills
CourseInstructor teaches
CourseStudent Registers for
Left to right: one to one, 1:1Right to left: one to one, 1:1
Left to right: one to many, 1:MRight to left: many to one, M:1
Left to right: many to many, M:MRight to left: many to many, M:M
Left to right: one to many, 1:MRight to left: many to one, M:1
Reading Cardinality and Modality
TranscriptStudenthas
Slide 18 Health IT Workforce Curriculum
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Many – to - One
• one through many notation on one side of a relationship and a one and only one
• zero through many notation on one side of a relationship and a one and only one
• one through many notation on one side of a relationship and a zero or one notation on the other
• zero through many notation on one side of a relationship and a zero or one notation on the other.
M:1
M:1
M:1
M:1
Slide 19 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
Many-to-Many
a zero through many on both sides of a relationship.
a one through many on both sides of a relationship.
a zero through many on one side and a one through many on the other.
Slide 20 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
One-to-One
a one and only one notation on one side of a relationship and a zero or one on the other.
A one and only one notation on both sides.
Slide 21 Health IT Workforce Curriculum
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ERD ExampleA doctor can be scheduled for many appointments, but may not have any scheduled at all. Each appointment is scheduled with exactly 1 doctor. A patient can schedule 1 or more appointments. One appointment is scheduled with exactly 1 patient. An appointment must generate exactly 1 bill, a bill is generated by only 1 appointment. One payment is applied to exactly 1 bill, and 1 bill can be paid off over time by several payments. A bill can be outstanding, having nothing yet paid on it at all. One patient can make many payments, but a single payment is made by only 1 patient. Some patients are insured by an insurance company. If they are insured, they can only carry insurance with one company. An insurance company can have many patients carry their policies. For patients that carry insurance, the insurance company will make payments, each single payment is made by exactly 1 insurance company.
Paragraph and diagram reprinted from : http://www2.cs.uregina.ca/~bernatja/crowsfoot.html
Slide 22 Health IT Workforce Curriculum
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ERD Example
A doctor can be scheduled for many appointments, but may not have any scheduled at all. Each appointment is scheduled with exactly 1 doctor.
Slide 23 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
ERD Example
A patient can schedule 1 or more appointments. One appointment is scheduled with exactly 1 patient.
Slide 24 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
ERD Example
An appointment must generate exactly 1 bill, a bill is generated by only 1 appointment.
One payment is applied to exactly 1 bill, and 1 bill can be paid off over time by several payments. A bill can be outstanding, having nothing yet paid on it at all.
Slide 25 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
ERD Example
One patient can make many payments, but a single payment is made by only 1 patient.
Some patients are insured by an insurance company. If they are insured, they can only carry insurance with one company. An insurance company can have many patients carry their policies.
For patients that carry insurance, the insurance company will make payments, each single payment is made by exactly 1 insurance company.
Slide 26 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
Maintenance
• Crow’s foot notation has become a defacto standard because of wide spread use
• The notation is documented in textbooks and other knowledge sources
• No changes are anticipated; there is no ongoing development of this methodology and no maintenance organization
Slide 27 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
In Summary
• Background of ERDs
• Process aspects covered by ERDs
• ERD use to represent static content
• We introduced the symbols and notation used in ERDs
• Worked through several examples reading a simple ERD
Slide 28 Health IT Workforce Curriculum
Version 1.0/Fal 2010Component 10/Unit 3f
References
1.) Chen, P. The Entity-Relationship Model: Toward a Unified View of Data (1976), ACM Transactions on Database Systems, 1:9-36.
2.) Bachman, C. W. (1969) Data Structure Diagrams. DATA BASE 1(2): 4-10
3.) Entity-relationship model Wikipedia topic, http://en.wikipedia.org/wiki/Entity_relationship_diagram#cite_note-0
Other readingCodd, E.F., A relational model of data for large shared databanks.
Communications of the ACM, vol 13 no 6. 1970. http://www.seas.upenn.edu/~zives/03f/cis550/codd.pdf